Optical mode splitter for MIMO transmission over multimode fiber

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This patent describes a specialized optical waveguide structure that acts as a mode splitter or combiner for use with multimode optical fibers. The invention facilitates the insertion and extraction of multiple distinct optical transmission modes into or out of a multimode fiber, enabling efficient multiple-input, multiple-output (MIMO) communications. The structure uses an adiabatic taper section to gradually separate or combine the spatial modes, matching the refractive index with the multimode fiber to minimize loss and using waveguide arrangements to naturally split or merge the modes.

Use CasesContent extracted from patent full text and abstract with AI.

• High-capacity optical data transmission systems for data centers and telecommunications networks.
• MIMO-based fiber-optic networks designed for extended reach (such as submarine cable links).
• Multi-channel high-speed fiber-optic interconnects.
• Research and development in advanced optical communications and integrated photonics.

BenefitsContent extracted from patent full text and abstract with AI.

• Significantly increases the data capacity of optical fibers by allowing simultaneous use of multiple spatial modes (Space Division Multiplexing).
• Reduces non-linear distortions and losses compared to single-mode or older coupling methods, enabling higher power launches and longer transmission distances.
• Enables more efficient and lower-complexity receiver designs by isolating modes physically before digital MIMO processing.
• Passive device design leads to low power consumption and inherent reliability.
• Supports scalable and flexible fiber-optic network configurations, enhancing performance without major infrastructure changes.

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Patent Abstract

The present document relates to optical transmission systems. In particular, it relates to multiple input, multiple output (MIMO) transmission over optical multimode fibers (MMF). More specifically, the present document relates to the coupling in and/or out of different optical modes of a MMF or a few mode fiber (FMF). An optical waveguide structure (400) configured to interconnect with a multimode fiber (401) supporting M optical modes, M>2, and configured to insert and/or isolate L subgroups of the M optical modes to and/or from the multimode fiber (401), L>1, is described. The L subgroups of optical modes each comprise less than M optical modes and the L subgroups in total comprise the M optical modes. The structure comprises a coupling section (402) configured to interconnect with the multimode fiber (401) and to transfer the M optical modes between the multimode fiber (401) and the optical waveguide structure (400), wherein the coupling section (402) has a refractive index matching a refractive index of the multimode fiber. Furthermore, the structure comprises a terminal section (415) opposite the coupling section (402) comprising L waveguides (403) which are configured to each provide and/or receive one of the L subgroups, respectively. In addition, the structure comprises a taper section (430) intermediate the coupling section (402) and the terminal section (410) and configured to adiabatically isolate each one of the M optical modes to one of the L waveguides (403); and/or merge the modes of the L waveguides (403) to the M optical modes.